Originally Posted by
Jim Becker
Biff, almost all of these spindles, air cooled or water cooled, are three phase which is needed for the variable speed and is also better suited to the task. Traditional routers used by some machines are certainly an exception, but any speed control is manual and done differently than with a spindle. The air requirement isn't necessary for a non ATC spindle other than for a counter-balance on the Z-axis to take load off the steeper or servo from the weight of the spindle. And that's just fixed air pressure...no real "usage". (My machine is so equipped) ATCs, however use air for the quick change mechanism clamping and some use additional air to supplement cooling as has been noted and there is some level of CFM required to support that, not just a particular air pressure as with a counter-balance.